/*
 * Copyright 2016 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.integration.transformer;

import java.io.ByteArrayOutputStream;
import java.io.Closeable;
import java.io.InputStream;

import org.springframework.integration.IntegrationMessageHeaderAccessor;
import org.springframework.messaging.Message;
import org.springframework.util.Assert;
import org.springframework.util.FileCopyUtils;

/**
 * Transforms an InputStream payload to a byte[] or String (if a
 * charset is provided).
 *
 * @author Gary Russell
 * @since 4.3
 *
 */
public class StreamTransformer extends AbstractTransformer {

	private final String charset;

	/**
	 * Construct an instance to transform an {@link InputStream} to
	 * a {@code byte[]}.
	 */
	public StreamTransformer() {
		this(null);
	}

	/**
	 * Construct an instance with the charset to convert the stream to a
	 * String; if null a {@code byte[]} will be produced instead.
	 * @param charset the charset.
	 */
	public StreamTransformer(String charset) {
		this.charset = charset;
	}

	@Override
	protected Object doTransform(Message<?> message) throws Exception {
		Assert.isTrue(message.getPayload() instanceof InputStream, "payload must be an InputStream");
		InputStream stream = (InputStream) message.getPayload();
		ByteArrayOutputStream baos = new ByteArrayOutputStream();
		FileCopyUtils.copy(stream, baos);
		Closeable closeableResource = new IntegrationMessageHeaderAccessor(message).getCloseableResource();
		if (closeableResource != null) {
			closeableResource.close();
		}
		return this.charset == null ? baos.toByteArray() : baos.toString(this.charset);
	}

}
